Sounds like your system is broken if it requires a reboot to get it to show up again.
that due to a bug in the FTDI drivers
known bug in the FTDI drivers
I use Ubuntu 10.04 32 bit with Arduino 0022. It works fine with Duemilanove (FTDI) and Uno.
Please enter a valid email to subscribe
We need to confirm your email address.
To complete the subscription, please click the link in the
email we just sent you.
Thank you for subscribing!
via Egeo 16